1. Field of the Invention
This invention relates to a method of treating photoresist materials applied on a semiconductor wafer and, more particularly, to a method of treating the developed positive photoresist image on a wafer in a chamber by employing ultraviolet irradiation.
2. Description of the Prior Art
As for the prior-art treatment of positive photoresist employing ultraviolet irradiation, exposing the photoresist to ultraviolet radiation is utilized in a treatment in which the same pattern as a mask pattern is formed on the photoresist film applied on a semiconductor wafer, etc., and recently attention has been paid to the application of this method to particular treatments such as the treatment of baking said photoresist film on a wafer.
The baking process is employed, between a process of "forming a photoresist pattern, exposing and developing the photoresist" and a process of "executing ion implantation, plasma-etching, etc.", and said process is composed of a heating process executed for improving the adhesiveness of the photoresist to a semiconductor wafer and heat-resistance of said photoresist. Studies have been made recently on a method in which ultraviolet rays are applied to the developed positive photoresist image after or during the baking process after "development process" so as to enhance the heat-resistance and plasma-resistance of the positive photoresist through the baking process in a shorter time. Theses method are described in a reference of H. Hiroaka and J. Pacansky: J. Vac, Sci. Tech. 19 (1981), and U.S. Application No. 923,250. When a light having a high ultraviolet intensity is applied to the photoresist at the beginning of exposure, however, organic solvent included in the photoresist is decomposed and evaporated, or photochemical reactions take place in the photoresist itself or in the chemical agents which are applied to a wafer as preliminary treatment for the good coating of the photoresist onto a wafer, and then a gas is generated from the photoresist, and this gas causes deformation or breakdown of a developed positive photoresist film.